The present invention relates to storage system for storing data in a plurality of disk drives and a disk control cluster forming part of the storage system.
When compared with the I/O performance of a main memory in a computer using a semiconductor storage as a storage medium, the I/O performance of a disk subsystem (which will be referred to as the subsystem, hereinafter) using a magnetic disk as a storage medium is small by about 3 or 4 figures. An effort has conventionally been put into reducing a difference in I/O performance between these semiconductor and disk storages, that is, improving the I/O performance of the subsystem. As one method of improving the I/O performance of the subsystem, there is known a system called a disk array wherein a subsystem is made up of a plurality of disk drives for storing data therein.
As shown in FIG. 2, for example, a prior art includes a plurality of channel IF units 11 for executing data transfer between host computers 3 and disk controllers 4, a plurality of disk IF units 16 for executing data transfer between disk drives 2 and the disk controllers 4, and shared memory units 20 for storing therein the data of the disk drives and control information on the disk controllers 4 (e.g., information relating to data transfer control within the disk controllers 4 and information for management of data to be stored in the disk drives 2). In each of the disk controllers 4, all the shared memory units 20 are arranged to be accessible by all the channel IF units 11 and disk IF units 16. In each disk controller 4, the channel IF units 11 and the disk IF units 16 are connected with the shared memory units 20 by an interconnection 30.
Each channel IF unit 11 has an interface for connection with the host computers 3 and a microprocessor (not shown) for controlling input and output from and to the host computers 3. Each disk IF unit 16 has an interface for connection with the associated disk drive 2 and a microprocessor (not shown) for controlling input and output from and to the disk drive 2. Each disk IF unit 16 also executes a RAID function.
Spread of the Internet involves radical increase of data to be handled in companies or firms, and thus it is necessary that a data center or the like store data beyond a data amount capable of being handled by a single disk controller. To this end, a plurality of such disk controllers 4 are installed to be connected with the host computers 3 via a SAN switch 5 as an interface with the host computers 3 as shown in FIG. 2.
Further, as the increase of the data amount involves increase of the number of such disk controllers 4 to be connected to the SAN switch 5, the management of the entire system (which is called the storage area network (SAN)) including the host computers 3 and SAN switch 5 becomes complicated. To cope with it, a SAN appliance 6 is connected to the SAN switch 5 to perform directory service over data to be managed by all the disk controllers 4 connected to the SAN switch 5 and to perform such operation that the host computers 3 look the plurality of disk controllers 4 like a single storage system. In other words, the SAN appliance 6 causes the host computers 3 to look storage areas offered by the disk controllers 4 like a single large storage area, and assigns necessary amounts of such a storage area to the host computers 3.
In another prior art as disclosed in JP-A-2001-256003, as shown in FIG. 23, a single storage system 1 is made up of a plurality of disk control clusters 1-1 to 1-n. Each disk control cluster includes a plurality of channel IF units 11 for executing data transfer between the associated host computer 3 and the associated disk control cluster, a plurality of disk IF units 16 for executing data transfer between the associated disk drive 2 and the associated disk control cluster, and shared memory units 25. An interconnection 31 is connected between the channel IF units 11, disk IF units 16 and shared memory units 25 in a plurality of disk control clusters 1-1 to 1-n. Stored in the shared memory units 25 are control information on the storage system. The shared memory units 25 are arranged so that the shared memory units can be accessed by all the channel IF units 11 and disk IF units 12 via an interconnection 31, so that exchange of the control information via the shared memory units 25 enables the plurality of disk control clusters to operate as a single storage system.
In large-scale companies such as typical banks, securities companies and telephone companies, computers and storages so far dispersed into local places tend to be centralized into a data center to form a computer system/storage system configuration, thus reducing costs necessary for the operation, maintenance and management of the computer system and storage system.
In such a tendency, a large-scale/high-end disk controller is required to support a channel interface for connection with hundreds of host computers (connectivity) and to support a storage capacity of hundreds of tera-bytes or more.
Meanwhile, with expansion of open market and spread of the storage area network (SAN) in these years, demands of appearance of disk controllers of a small-scale configuration (small-scale rack) with rich functions/high reliability similar to the large-scale/high-end disk controller have been stronger.
For the former demand, it is considered to connect a plurality of such conventional large-scale/high-end disk controllers to form a huge storage configuration.
For the latter demand, it is considered to minimize its rack in a minimum configuration model of the conventional large-scale/high-end disk controller. When a plurality of such minimized controllers are connected, further, a storage system is considered which can support a medium-to-large scaled configuration supported by the conventional disk controller.
As has been mentioned above, a storage system is required to have a small- to huge-scale configuration compatible with a reliable architecture with a good scalability. To this end, such a storage system is required that a plurality of disk controllers can be clustered and be operated as a single system.
In the prior art shown in FIG. 2, the plurality of disk controllers 4 are connected to the host computers 3 via the SAN switch 5 so that the SAN appliance 6 causes the host computers 3 to look the disk controllers 4 like a single storage system.
However, the prior art has a problem that, since the plurality of disk controllers 4 are operated as a single system under control of software operating on the SAN appliance 6, the prior art is lower in reliability and availability than the conventional single large-scale disk controller. Another problem is that, since the SAN appliance 6 searches the disk controllers 4 for data present therein and demanded by the host computers 3, the performance of the prior art becomes low.
When an error occurs in the channel IF units 11 of one disk controller 4 and it become impossible to access data of the disk drive connected to this disk controller, furthermore, it becomes necessary to once stop the access from the host computer 3 to the disk controller 4 and to exchange the channel IF unit 11, with the result that this disadvantageously affects an application program running under control of the host computer 3.
The prior art shown in FIG. 23 provides a storage system with a high scalability wherein the plurality of disk control clusters exchange control information via the shared memory units 25 and operate as a single storage system.
This prior art however has a defect that its bad handleability to users. In other words, in order to enhance the performance, it is necessary that a storage area to be assigned to the host computer 3 be a storage area on the disk drive 2 connected to the disk control cluster connected with the host computer 3. Further, for the purpose of preventing impossible access to the disk control cluster due to an interface error between the host computer 3 and disk control cluster, it becomes necessary to connect connection paths from one host computer to the plurality of disk control clusters. In addition, even when the plurality of connection paths are connected, it is impossible to perform switching between the connection paths without notifying it to the host computer.
It is therefore an object of the present invention to provide a storage system with a good scalability which can be compatible with an identical high reliability/high performance architecture from a small scale configuration to a huge scale configuration.
A specific object of the present invention is to provide a storage system into which a plurality of disk controllers are combined and has a high reliability, high performance and good handleability.
The above object is attained by providing a storage system which includes a plurality of disk control clusters, each of the plurality of disk control clusters having one or a plurality of channel interface units having interfaces with host computers, one or a plurality of disk interface units having interfaces with disk drives, and a local shared memory unit for storing data to be read/written from/to the disk drives, control information about transfer of data and management information about the disk drives, the channel interface units executing data transfer between the interfaces with the host computers and the local shared memory units in response to a read/write request from the host computers, the disk interface units executing data transfer between the disk drives and the local shared memory units to read/write the data;
a global information control unit for storing the data to be read/written from/to the disk drives and the management information about the disk control clusters;
an interconnection connected between the plurality of disk control clusters; and
a switch for connecting the channel interface units in the plurality of disk control clusters,
wherein the switch has a memory to which the management information stored in the global information control unit is copied.
The above object is further attained by providing a storage system wherein connection units for connecting the channel interface units, the disk interface units and the local shared memory unit in one of the disk control clusters are connected to corresponding connection units of the other disk control clusters by means of the interconnection, and the global information control unit is connected to the interconnection and the switch.
The object is attained also by providing a storage system wherein the channel interface units and the disk interface units are directly connected to the local shared memory unit in each of the disk control clusters, the local shared memory unit in the disk control cluster is connected to the local shared memory units in the other disk control clusters by means of the interconnection, and the global information control unit is connected to the interconnection and the switch.
The object is attained also by providing a storage system wherein the channel interface units and the disk interface units are connected directly to the local shared memory unit in each of the disk control clusters, connection units for connecting the channel connection units and the disk interface units in one of the disk control clusters are connected to corresponding connection units of the other disk control clusters by means of the interconnection, and the global information control unit is connected to the interconnection and the switch.
The object is attained also by providing a storage system which includes,
a plurality of disk control clusters, each of the plurality of disk control clusters having one or a plurality of channel interface units having interfaces with host computers, one or a plurality of disk interface units having interfaces with disk drives, and a local shared memory unit for storing data to be read/written from/to the disk drives, control information about transfer of data and management information about the disk drives, the channel interface units executing data transfer between the interfaces with the host computers and the global information control unit in response to a read/write request from the host computers, the disk interface units executing data transfer between the disk drives and the global information control unit to read/write the data;
an interconnection connected between the plurality of disk control clusters; and
a switch for connecting the channel interface units in the plurality of disk control clusters,
wherein the switch has a memory to which the management information stored in the global information control unit is copied.
The object is attained also by providing a storage system wherein connection units for connecting the channel interface units and the disk interface units in one of the disk control clusters are connected to corresponding connection units of the other disk control clusters by means of the interconnection, and the global information control unit is connected to the switch by means of the interconnection.
The object is attained also by providing a storage system which includes a plurality of disk control clusters, each of the plurality of disk control clusters having one or a plurality of channel interface units having interfaces with host computers, one or a plurality of disk interface units having interfaces with disk drives, and a local shared memory unit having first and second memories, the first memory storing data to be read/written from/to the disk drives, the second memory storing control information about data transfer between the channel interface units and the disk interface units and the first memory and also storing management information about the disk drives, the channel interface units executing the data transfer between the interfaces with the host computers and the first memory of the local shared memory units in response to a read/write request from the host computers, the disk interface units executing the data transfer between the disk drives and the first memory of the local shared memory units to read/write the data;
a global information control unit for storing management information about the disk control clusters;
two first and second different interconnections for interconnecting the plurality of disk control clusters; and
a switch for connecting the channel interface units in the plurality of disk control clusters,
wherein the switch has a memory to which the management information stored in the global information control unit is copied.
The object is attained also by providing a storage system wherein the channel interface units and the disk interface units in each of the disk control clusters are connected directly to the second memory in the local shared memory unit in the disk control cluster, first connection units for connecting the channel interface units and the disk interface units in one of the disk control clusters are connected to corresponding first connection units of the other disk control clusters via the first interconnection, second connection units for connection the channel interface units, the disk interface units and the first memory of the local shared memory unit in one of the disk control clusters are connected to corresponding second connection units of other disk control clusters via the second interconnection and the global information control unit is connected to the first interconnection and the switch.
Other objects of the present application and how to solve the objects will become apparent from the DETAILED DESCRIPTION OF THE EMBODIMENTS and the attached drawings.